The invention relates to an apparatus and a method for the trenchless laying of pipework underground.
The primary purpose of such apparatuses and/or methods is the laying of line systems, such as drains, for example under roads or pavements without at the same time having to dig up the road surface or pavement. As a drilling, bursting or widening apparatus moves through the earth, it forces the earth aside or removes it and leaves behind an underground. channel into which a supply line can then be drawn as a follow-up pipe.
A drilling. apparatus of this type is known from Genaan Published Application 196 08 980. It comprises a platform with a hydraulic piston/cylinder unit which reciprocally moves a traveler in a linear manner. The traveler is connected to a locking pawl which, during the advance of the traveler, engagesbehind a rung of a ladder-type linkage and so moves the linkage, connected to the drilling head, forward in the drilling direction in accordance with the stroke of the hydraulic piston/cylinder unit At the end of to stroke, the locking pawl is automatically released from the rung and the traveler moves back automatically into its initial position, in which the locking pawl again engages behind a rung. The disposal or supply line which is to be laid is secured to the drilling head.
The line, in this method, is screwed or plugged together, for example, from individual pipe sections which are drawn in during the forward advance. In particular, the screwing of the pipe sections entails an additional working effort and causes problems because the screw connection can easily be contaminated and because the screw connection always results in a surface irregularity at the point of the butt joint
In plug-in Systems the pipe sections, if their connections are not resistant to traction, have to be drawn into the tube made in the earth via a traction means, and have first to be threaded onto the traction means. The pipe sections that are drawn in have to be shorter than the length of the launch pit or the launch shaft In many cases drainage shaft have a diameter of only 1 m. In practice, only pipe sections 0.7 m in length can be drawn in from such constricted shaft, in other words the newly laid pipe has a socket joint every 0.7 m which may develop leaks. This pipe joint is always a weak point, since its wall thickness may not be greater than that of the actual pipe.
In order to avoid this disadvantage, PE pipes wound into coils are used. A disadvantageous effect of these pipes is that they are relatively rigid and have only a limited bending radius. The consequence of this is that the volume of the coil is very great and the pipes snap back powerfullyxe2x80x94which is associated with a high risk of injury to the workersxe2x80x94and that the launch pit from which the drilling begins must have a certain size so that the PE pipe can be unwound from the roll situated at ground level and drawn into the microtunnel without being bent bow the admissible bending radius, causing damage to the pipe.
Especially in the laying of disposal or supply lines in cities, the dense building development means that it is often impossible to excavate sufficiently large pits for coiled pipes to be able to be used as follow-up pipes.
In addition, it is desirable for cost reasons to use as launch pits existing manholes which generally have an internal diameter of 1 m and an aperture having a diameter of about 80 cm.
In order to avoid these disadvantages what are known as folded pipes have been developed (cf. Series of publications from the Institute for Pipework Engineering at Oldenburg Technical University, Volume 14 xe2x80x9cFehler in der Kanalsanierung [Errors in sewer renovation]xe2x80x9d, Vulkan-Verlag, Essen, 1998). These pipes are notable for the fact that their diameter is reduced by their being folded to the cross section of a xe2x80x9cUxe2x80x9d or xe2x80x9cCxe2x80x9d. As a result, these pipes are much more flexible than conventional circular pipes and so easier to handle. In the laying of these pipes, a folded pipe is initially drawn into an old line. In a second step it is brought into its final shape with the use of hot media subjected to the action of pressure.
This method, however. is suitable only for the laying of new pipes in existing ones which are not destroyed in the process. This means that the pipes are merely made good but not replaced, since the old line remains in place and is merely lined with an expansible or expanded pipe. It is, therefore, always necessary to accept a reduced diameter by comparison with the old line. In addition, much energy is needed to provide the hot media subjected to the action of pressure, which makes the method expensive. Furthermore, the control of the widening process is very laborious if it is desired to avoid damage to the new pipe.
In the light of this background the object of the invention is to provide an apparatus and a method for the trenchless laying of pipework which can be implemented from pits of small dimensions, preferably existing inspection shafts of sewage system , and perferably permits the use of a compactly wound coiled or follow-up pipe.
The achievement of this object is based on the idea of using an easily transported and handled preformed material, especially a performed pipe of small cross section, which is given its final, preferably circular cross section only on site, for example in a narrow launch pit.
On this basis, the use is proposed of a preformed pipe of reduced cross section which, before being drawn into the ground, is continuously brought into shape by means of a gauge. Bringing into shape means that the pipe is brought to the intended final cross section on site or before entry into the ground, and is not shaped in its entirely after it has been laid. Such a preformed pipe offers the advantage of much smaller possible bending radii than a pipe of circular cross section. A PE pipe of U-shaped cross section is preferably used. Whereas a PE pipe of 200 mm diameter can be bent only to a radius of 6 m (equal to 30xc3x97d), a preformed pipe of the same diameter in the widened state having a U-shaped cross section can be bent to a radius of 0.9 m, in other words 6.1 m less, without sustaining damage.
The gauge which widens the PE pipe, folded for example in a U-shape to a smaller cross section, to a circular cross section before its entry into the ground is located in a stationary manner in the launch pit and is so designed that it can absorb the axial tension forms acting on the preformed pipe.
Instead of a U-shaped preformed pipe, it is also possible to use an elliptical preformed pipe in the form of a coil. It is also conceivable to use a pipe of smaller diameter which is stretched to a larger diameter in the launch pit
The gauge may be heatable. It is however also conceivable to place the gauge, together with the preformed pipe section located immediately in front of it, in a bath filled with a temperature-controlled fluid, or to lay a heating collar around the gauge together with the pipe section, so that the pipe passes through between the gauge and the heating collar. The warming of the pipe permits non-destructive and low-energy widening to the final diameter.
The invention makes it possible to lay, instead of old lines, lines whose diameter is greater than that of the old line.
A cooling system may also be used to cool the previously warmed and shaped and/or widened pipe run and so bring it back to its original strength if the new pipe, after entry into the ground, is exposed to the full pressure of the ground and it is desired to prevent the shards of the old burst pipe from failing down.
In addition, the gauge can also be provided with lubricant nozzles In order to reduce the friction between gauge and PE pipe, using a conventional lubricant Similarly, the annulus space between the PE pipe and the ground can be filled with a lubricant and/or filler which simultaneously acts as a coolant
Guide points may also be arranged in the area of entry of the pipe into the ground so that the pipe is bent to a preselected radius in that area. Such guide points are described in German Application 197 14 7054. As a result of this enforced guidance, which preferably consists of rollers, the pipe can be fed non-destructively in such a way that it extends in a space-saving manner in the launch shaft, so that shaft size can be further minimized.
The invention can be used both for introducing a new disposal or supply line into an existing line and for the laying of a new line instead of an old pipe which is demolished by means of a bursting head during laying and whose shards are displaced laterally or removed, and also in the laying of new lines.